Could a daily cup of coffee protect the brain against depressive symptoms?

A new study evaluating the mental health impacts of popular hot beverages found that while drinking tea had no connection to mood, consuming coffee might relate to fewer overall symptoms of depression. The research, published in Scientific Reports, analyzed the daily beverage habits of nearly 2,000 adults to understand how these drinks align with psychological well-being.

Mental health conditions affect millions of people globally, often disrupting daily life and making it difficult to maintain normal routines. Depression involves a persistently low mood, deep sadness, and a loss of interest in typical activities. Anxiety manifests as overwhelming worry or nervous tension that feels impossible to control.

Rates of both psychological conditions are rising in many parts of the world, including the Middle East. Medical professionals treat these conditions with various behavioral therapies and prescription medications. Researchers also want to identify daily lifestyle factors that might prevent these symptoms from developing in the first place.

Nutrition is a major target for scientists looking at modifiable health habits. The foods and drinks people consume daily supply the cellular building blocks for the brain chemicals that regulate mood. Because coffee and tea are two of the most widely consumed beverages on the planet, nutritionists want to know if they provide any mental health benefits.

Previous investigations into coffee and tea have produced mixed results. Some scientific papers report that drinking these beverages lowers the odds of depression. Other studies suggest they worsen mental health symptoms or have no effect at all.

Free daily newsletter

These inconsistent results might stem from differences in how various cultures prepare and consume their drinks. Much of the existing research originates from Western countries and East Asia. Studies focusing specifically on Middle Eastern populations remain relatively scarce.

In Iran, tea is traditionally the primary daily beverage and is deeply embedded in the local culture. Over the last decade, coffee has become increasingly popular, though total consumption remains low compared to the United States or Europe. This unique cultural shift creates an ideal setting to observe how these two different drink habits correspond to psychological distress.

Mohammad Matin Mahjourian, a researcher at the Tehran University of Medical Sciences, led a team to investigate this exact topic. The team wanted to isolate the dietary patterns of Iranian adults and compare them with self-reported mental health scores.

The researchers conducted a cross-sectional study. This type of research takes an informational snapshot of a specific population at a single point in time. The study included 1,994 adults recruited from a larger health project spanning five major cities across Iran.

The primary goal was to gather detailed information about what these individuals ate and drank over the previous year. To achieve this, trained interviewers sat down with each participant and filled out a specialized dietary questionnaire. The survey listed more than 100 food items and asked participants to estimate their typical portion sizes alongside how often they ate them.

The scientists placed participants into separate categories depending on their answers. For tea, the individuals fell into three groups based on their daily intake: less than one cup, one to two cups, or two or more cups. Coffee drinkers were divided more simply into those who consumed at least one cup a day and those who drank none.

To measure psychological well-being, the team used translated and validated mental health questionnaires. The participants answered a series of questions ranking their emotional states on a simple numerical scale. Higher scores indicated a greater presence of depressive or anxious symptoms.

Analyzing the raw numbers revealed immediate differences between the groups of beverage drinkers. In the initial look at the data, the tea categories showed no distinct variations in mood scores. People who drank multiple cups of tea experienced the exact same rates of depression and anxiety as those who drank very little.

Coffee consumption presented a different picture in the unadjusted data. The researchers noticed that individuals who drank at least one cup of coffee a day had 40 percent lower odds of reporting depressive symptoms compared to non-drinkers. They also had 27 percent lower odds of experiencing intense anxiety.

In population science, an initial association does not tell the whole story. Coffee drinkers often lead different lives than non-drinkers. The survey answers showed that the coffee consumers in this specific area tended to be more physically active, had higher levels of education, and possessed greater financial resources.

These outside variables are known as confounders because they can falsely create or mask a mathematical relationship between two factors. For example, having a higher income might be the real reason a person feels less depressed, rather than their morning coffee habit. To find the isolated impact of the beverages, the scientists adjusted their equations to remove the influence of these confounders.

The researchers applied several layers of statistical adjustments. They controlled for age, sex, total daily calories, smoking status, and physical activity. They also factored in specific nutrients known to support brain health, such as folate, iron, magnesium, zinc, and vitamin B12.

Once the team accounted for all these diet and lifestyle factors, the initial findings shifted heavily. The link between tea and mood remained completely absent. For zeroing in on coffee, the adjustment entirely erased the association with lowered anxiety.

The mathematical connection between coffee and lowered depression weakened as well. Ultimately, the adjusted results were not statistically significant for depression either. Rather than showing a definitive protective effect, the math only pointed toward a subtle tendency that coffee drinkers might have slightly fewer depressive symptoms.

Even though the final numbers only suggested a subtle trend, scientists have several biological theories about why coffee might influence mood over time. The primary active component in coffee is caffeine. Caffeine is an active chemical molecule that readily travels from the bloodstream directly into the brain.

Once inside the brain, caffeine binds to specific structures on the surface of brain cells known as adenosine receptors. Under typical conditions, a molecule called adenosine matches with these receptors throughout the day. When adenosine connects, it signals the nervous system to slow down, making a person feel sleepy and relaxed.

Caffeine intercepts this process by taking the spot of adenosine without triggering the tiredness signal. By blocking adenosine, caffeine essentially removes the brakes on the nervous system. This allows other naturally occurring brain chemicals to increase their activity.

Two of the signaling chemicals that increase in the presence of caffeine are dopamine and norepinephrine. Dopamine is heavily involved in human motivation, reward, and the experience of pleasure. Increasing dopamine activity is one way the brain elevates a person’s mood and combats feelings of sadness.

Norepinephrine acts similarly to adrenaline, increasing a person’s overall alertness and physical focus. The simultaneous boost of both dopamine and norepinephrine is what gives coffee drinkers their characteristic morning jolt. Over the short term, this chemical cascade functions as a mild mood enhancer.

The long-term effects of daily caffeine use are quite different, which might explain why population surveys rarely show massive mental health benefits in heavy drinkers. The human body is highly adaptable. When caffeine routinely blocks the normal sleepiness signals, the brain attempts to restore its resting balance.

To compensate for the blockade, the brain generates entirely new adenosine receptors. With more receptors available, more caffeine is required to achieve the exact same stimulating result. This physiological adaptation is known medically as tolerance.

Because regular coffee drinkers build tolerance, their daily habit might simply restore their baseline mood rather than continuously elevating it above normal levels. Skipping their daily cup leaves their new abundance of adenosine receptors completely open, resulting in sluggishness and irritability. This biological cycle helps explain the mixed outcomes seen in massive dietary surveys that cover long stretches of time.

Another relevant biological factor involves genetics. Every person possesses a slightly different genetic code, which dictates how quickly their internal organs process and remove molecules from the bloodstream. Some individuals metabolize caffeine rapidly, experiencing a short and pleasant burst of energy.

Others are slow metabolizers. For them, caffeine lingers in the body for many consecutive hours. They are more likely to experience jittery sensations, insomnia, and an elevated heart rate. Over time, these negative physical reactions can contribute to psychological distress, entirely negating any initial mood improvement.

While the Iranian study provides a helpful look into a unique population, the authors highlighted several limitations to their work. The most prominent weakness is the cross-sectional study design. Evaluating people at a single historical moment makes it impossible to determine the true direction of the relationship.

For instance, scientists cannot say whether drinking coffee directly prevents depression. The reverse scenario remains equally possible. People suffering from clinical depression might naturally lose the physical motivation to prepare a morning coffee, or they might avoid the beverage if it triggers their general anxiety.

The reliance on human memory also poses a research challenge. Participants had to think back over an entire year to estimate their average food and drink intake. People frequently overstate or understate their true habits when relying on long-term recall.

The research team also excluded individuals with severe chronic illnesses such as kidney disease, liver disorders, or extreme immune system abnormalities. While leaving out these patients helped isolate the effects of the diet itself, it means the population studied was generally healthier than average. The final numbers might not apply to people dealing with heavy physical ailments.

Finally, the actual number of regular coffee drinkers found in the study was relatively small. Out of almost 2,000 total participants, only 348 consumed coffee daily. A smaller group size limits the mathematical ability of statistical software to detect subtle health relationships.

To build on this foundation, researchers will need to design prospective cohort studies. In a prospective cohort, scientists recruit a large group of healthy volunteers and track their health habits continuously over many years. By monitoring health changes as they happen, researchers can establish a more accurate timeline of human cause and effect.

The study, “Tea and Coffee Consumption in Relation to Depression and Anxiety Symptoms: Findings from the Multicentric LIPOKAP Study,” was authored by Mohammad Matin Mahjourian, Ghazaleh Bahrami, Noushin Mohammadifard, Fahimeh Haghighatdoost, Farid Najafi, Hossein Farshidi, Masoud Lotfizadeh, Tooba Kazemi, Hamidreza Roohafza, and Nizal Sarrafzadegan.